Gay-rights activists praised the ruling in a lawsuit pursued by the Northern Ireland Human Rights Commission. But Health Minister Edwin Poots, an evangelical Protestant opposed to gay partnerships, said the government would appeal. He called the ruling against the best interests of children.

Belfast High Court Justice Seamus Treacy ruled that the law clearly violated European human rights laws on privacy and discrimination.

Other parts of the United Kingdom already permit gay and unmarried heterosexual couples to adopt children. But Northern Ireland’s law restricts applicants to married couples and single adults, including gay people. Northern Ireland, like the rest of the UK, legalized civil partnerships for gay people in 2005.

Michael O’Flaherty, Northern Ireland’s chief commissioner for human rights,
said that “given the high numbers of children in care, who need a family in Northern Ireland, the importance of this case in widening the pool of prospective parents cannot be overstated.’’ Over 2,500 children in Northern Ireland are in state care awaiting adoption.

John O’Doherty, director of a Northern Ireland gay-rights group called the Rainbow Project,
accused Poots of ‘‘allowing his personal prejudices to influence his public responsibilities.’’